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This question is not specific to TeX and derivatives, but I feel that this community is the best to answer it.

Should the letter lambda (λ) be typeset upright or in italics in the following situations occurring in lambda-calculus?

  1. in lambda-expressions such as: λ x . x+2
  2. in names such as: λ-calculus, λ-abstraction
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up vote 2 down vote accepted

The fundamental book on lambda calculus has been typeset with LaTeX, using Knuth's Computer Modern fonts. Some pages of it can be seen at this link and the lambda is the standard italic one.

This said, I believe it's a question of personal preference which can depend on the font used for the document one is preparing.

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Though I find it difficult to tell upright λ and italic λ apart. That said, you have more familiarity with the fonts and have better judgment than I do on this. – Lover of Structure Feb 28 '13 at 20:16
@LoverofStructure One might object that Barwise and the other authors (or the publisher) used the only lambda they had available, that is, the math italic lambda designed by Knuth. One should ask them. However, in pure mathematics, the "upright operator symbols" convention is rarely enforced and anarchy reigns. :) – egreg Feb 28 '13 at 20:20
Yeah, I prefer upright λ to italic λ [<- in italics here!] for this purpose. Italics sometimes look a little squeezed on the page. – Lover of Structure Feb 28 '13 at 20:26

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